Process for producing a transparent optical element, optical component involved in this process and optical element thus obtained

ABSTRACT

To produce a transparent optical element, the process starts with the production of an optical component having at least one transparent array of cells that are juxtaposed parallel to one surface of the component, each cell being hermetically sealed and containing a substance having an optical property. This optical component is then cut along a defined contour on its surface, corresponding to a predetermined shape of the optical element. Preferably, the array of cells constitutes a layer having a height of less than 100 μm perpendicular to the surface of the component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is being filed as a divisional application of U.S.application Ser. No. 11/173,898, filed on Jul. 1, 2005, which claims thebenefit of French Patent Application No. 04 13537, filed Dec. 17, 2004,and French Application No. 04 07387, filed Jul. 2, 2004. The contents ofthese applications are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

The present invention relates to the production of transparent elementsincorporating optical functions. It applies especially to the productionof ophthalmic lenses having various optical properties.

Ametropia-correcting lenses are conventionally manufactured by theforming of a transparent material having a refractive index higher thanthat of air. The shape of the lenses is chosen so that the refraction atthe material/air interfaces causes suitable focussing onto the retina ofthe wearer. The lens is generally cut so as to fit into a spectacleframe, with appropriate positioning relative to the pupil of thecorrected eye.

It is known to vary the refractive index within the material of anophthalmic lens, thereby making it possible to limit the geometricalconstraints (see for example EP-A-0 728 572). This method was proposedabove all for contact lenses. The index gradient is obtained for exampleby diffusion, selective irradiation or selective heating during themanufacture of the solid object constituting the lens. Although thisprovides for manufacture for each treatable case of ametropia, themethod does not lend itself well to mass production. Otherwise, it ispossible to manufacture, on an industrial scale, series of objects ofgraded index, to select that one which is closest to the one suitablefor an eye to be corrected, and to carry out a re-forming operation onit, by machining and polishing, in order to adapt it to this eye. Inthis case, the need to carry out a re-forming operation on the lensesmeans that a great deal of the attraction of the method over theconventional methods is lost.

Patent Application US 2004/0008319 proposes to modulate the refractiveindex parallel to the surface of a lens, such as a spectacle lens, usingink-jet heads of the kind employed in printers. These heads arecontrolled so as to deposit drops of solutions of polymers havingdifferent indices onto the surface of the object so as to obtain thedesired variation of the index over the surface. The polymers are thensolidified by irradiation or solvent removal. Control of the physicalphenomena of interaction between the drops and the substrate, duringboth deposition and solidification, makes this method very difficult toput into practice. Furthermore, its use on a large scale is problematicsince, here again, the index modulation is obtained during themanufacture of the solid object constituting the lens, and thesubsequent customization assumes that a re-forming operation is carriedout on the lens.

Another field of application of the invention is that of photochromiclenses. The structure of such a lens incorporates a layer whose lightabsorption spectrum depends on the light received. The photochromic dyeof this layer is usually solid, although it is known that liquids orgels have superior properties, especially in terms of speed of reactionto the variations in luminosity.

Nevertheless, lenses are known in which the photosensitive dye is aliquid or a gel, spacers being provided in the thickness of the layer inorder to define the volume occupied by the dye between adjacenttransparent layers, with an impermeable barrier around the periphery ofthis volume. Such a lens is manufactured for a specific spectacle frame.It is not possible to cut the lens in order to fit it to another frame.It is also difficult to adapt it to the ametropia of a lens to becorrected.

It may also be beneficial to vary the light absorption parallel to thesurface of the lens and/or to make this absorption dependent on thepolarization of the light. Among other types of ophthalmic lenses towhich the invention may apply, mention may be made of active systems inwhich a variation in an optical property results from an electricalstimulus. This is the case of electrochromic lenses, or else lenseshaving variable refractive properties (see for example U.S. Pat. No.5,359,444 or WO 03/077012). These techniques generally make use ofliquid crystals or electrochemical systems.

Among these various types of lenses, or others that are not necessarilylimited to ophthalmic optics, it would be desirable to be able toprovide a structure that allows one or more optical functions to beintroduced in a flexible and modular manner, while still maintaining thepossibility of cutting the optical element obtained, with a view toincorporating it into a specified spectacle frame or one chosenelsewhere, or into any other means of holding said optical element inplace.

One object of the present invention is to meet this requirement. Anotherobject is to be able to produce the optical element on an industrialscale under appropriate conditions.

SUMMARY OF THE INVENTION

The invention thus proposes a process for producing a transparentoptical element, comprising the following steps:

-   -   producing an optical component having at least one transparent        array of cells that are juxtaposed parallel to one surface of        the component, each cell being hermetically sealed and        containing a substance having an optical property; and    -   cutting the optical component along a defined contour on said        surface, corresponding to a predetermined shape of the optical        element.

The cells may be filled with various substances chosen for their opticalproperties, for example those associated with their refractive index,their light absorptivity or polarization, their response to electricalor light stimuli, etc.

The structure therefore is adapted for many applications, particularlythose involving variable optical functions. It implies dividing thesurface of the optical element into discrete pixels, thereby offeringgreat flexibility in the design, but also in the use of the element.

In particular, it is noteworthy that the optical component can be cut tothe desired peripheral shapes, allowing it to be incorporated and fittedto various holding supports such as, for example, a spectacle frame or ahelmet. The process may also include, without affecting the integrity ofthe structure, a step in which the optical component is drilled so as tofasten the optical element to its holding support.

The layer formed by the array of cells will advantageously have a heightof less than 100 μm. According to various embodiments of the invention,this height is preferably between 10 μm and 50 μm, or between 1 μm and10 μm. In particular, it may be equal to about 5 μm.

Within the context of the invention, the array of juxtaposed cells ispreferably configured so that the fill factor τ, defined as the areaoccupied by the cells filled with the substance, per unit area of thecomponent, is greater than 90%. In other words, the cells of the arrayoccupy at least 90% of the area of the component, at least in a regionof the component that is provided with the array of cells.Advantageously, the fill factor is between 90% and 99.5% inclusive, andeven more preferably the fill factor is between 96% and 98.5% inclusive.

In order for the pixel structure not to cause undesirable diffractioneffects, it is possible to make the dimensions of the cells so as tomatch the wavelengths of the spectrum of the light in question. Thegeometry of the array of cells is characterized by dimensionalparameters that may in general relate to the dimensions of the cellsparallel to the surface of the optical component, to their heightcorresponding to the height h of the walls separating them, and to thethickness d of these walls, measured parallel to the surface of thecomponent. The dimensions of the cells parallel to the surface definethe area σ of a cell. In the simple case where the cells are square withsides of length D (FIG. 4), this area is given by σ=D², and the fillfactor τ is approximately given by D²/(D+d)². The expressions for σ andτ are easily obtained for any other spatial organization of the cells.

The main source of defects in an array of cells may consist of the gridof walls. These walls are the source of a transparency defect of theoptical component. In the meaning of the invention, an optical componentis said to be transparent when an image observation through this opticalcomponent is perceived without significant contrast reduction, that isto say when an image formation through the optical component is obtainedwithout impairing the image quality. Thus, the walls which separate theoptical component cells interact with light, by diffracting this light.In the meaning of the invention, diffraction is defined as being thelight spreading phenomenon which is observed when a luminous wave ismaterially bound (“Optique—Fondement et applications”—J. P.Pérez—Dunod—7^(éme) edition—Paris 2004—Page 262). More specifically, thelight energy impinging a wall is concentrated in a solid angle. Becauseof this, a light emitting point is no longer perceived as a pointthrough an optical component which comprises such walls. Thismicroscopic diffraction appears macroscopically like diffusion. Thismacroscopic diffusion, or incoherent diffusion, appears as a milkyrendering of the pixellized structure of the optical component, and soas a contrast reduction of an image observed through the structure. Thiscontrast reduction may be considered as a transparency reduction, asdefined above. Such behaviour of macroscopic diffusion cannot beaccepted for an optical element obtained from a pixellized opticalcomponent according to the invention, in particular for an ophthalmiclens which has to be transparent and should not incorporate any cosmeticdefect which could impair the vision of the wearer of this lens. Bydimensioning the cells judiciously, it is possible to reduce thediffracted energy for a given wavelength.

Thus, within the context of the invention, it will be possible to givethe cells dimensions of greater than 1 μm parallel to the surface of thecomponent. In particular, these cell dimensions parallel to the surfaceof the component may be between 5 μm and 100 μm. In the application toophthalmic optics, it may be desirable to avoid excessively large cells,something which would give the surface of the lenses a visible texture.Advantageously, the cells may have a dimension of between 10 μm and 40μm.

Parallel to the surface of the component, the cells will preferably beseparated by walls with a thickness of between 0.10 μm and 5 μm. In afirst embodiment of the invention, the walls have a thickness of between0.10 μm and 5 μm, and preferably between 0.10 μm and 0.35 μm, so thatthey also produce virtually no undesirable diffractive effects in thevisible spectrum. Such thin walls may provide a very high fill factor τof the optical surface with the substance having a beneficial opticaleffect.

In a second embodiment, the walls have a thickness of between 0.40 μmand 2.00 μm. For example, this thickness may be equal to 1.00 μm. In athird embodiment, the walls have a thickness of between 2.00 μm and 3.5μm, it being possible for example for this to be equal to 3.0 μm. Theconstituent material of the cell walls will be chosen in such a way thatthe cells will no longer be discernible from the material with whichsaid cells are filled. The expression “not discernible” is understood tomean that there is no visible scattering, no visible diffraction and noparasitic reflections. In particular, this may be achieved in practiceby suitably adjusting the refractive index and the absorption.

The array of cells may be formed directly on a rigid transparentsubstrate, or within a flexible transparent film that is subsequentlytransferred onto a rigid transparent substrate. Said rigid transparentsubstrate may be convex, concave or plane on that side which receivesthe array of cells.

In one method of implementing the process, the substance having anoptical property contained in at least some of the cells is in the formof a liquid or gel. Said substance may especially have at least one ofthe optical properties chosen from coloration, photochromism,polarization and refractive index.

It may especially be in the form of a liquid or gel and it mayincorporate a photochromic dye, thereby making it possible for aphotochromic element with a very rapid response to be convenientlyproduced.

For the application to the manufacture of corrective lenses, it isnecessary for different cells of the optical component to containsubstances having a different refractive index. Typically, therefractive index will be adapted so as to vary over the surface of thecomponent according to the estimated ametropia of an eye to becorrected.

For the application to the manufacture of optical lenses having apolarization optical property, the cells of the optical component willespecially contain liquid crystals that may or may not be combined withdyes.

One subject of the present invention is also a process for producing anoptical component as defined above, which comprises the formation, on asubstrate, of a grid of walls for defining the cells parallel to saidsurface of the component, the collective or individual filling of thecells with the substance having an optical property in the form of aliquid or gel, and the closing of the cells on their opposite side fromthe substrate.

The array of cells of the optical component may include several groupsof cells containing different substances. Likewise, each cell may befilled with a substance having one or more optical properties asdescribed above. It is also possible to fill several arrays of cellsover the thickness of the component. In this embodiment, the arrays ofcells may have identical or different properties within each layer, orthe cells within each array of cells may also have different opticalproperties. Thus it is possible to envisage having a layer in which thearray of cells contains a substance for obtaining a refractive indexvariation and another layer or array of cells contains a substancehaving a photochromic property.

Another aspect of the invention relates to an optical component used inthe above process. This optical component comprises at least onetransparent array of cells that are juxtaposed parallel to one surfaceof the component. Each cell is hermetically sealed and contains asubstance having an optical property. Preferably, the cells areseparated by walls with a height of less than 100 μm, and may havedimensions of greater than 1 μm parallel to the surface of thecomponent.

Yet another aspect of the invention relates to a transparent opticalelement, especially a spectacle lens, produced by cutting such anoptical component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an optical component according to theinvention;

FIG. 2 is a front view of an optical element obtained from this opticalcomponent;

FIG. 3 is a schematic sectional view of an optical component accordingto the invention;

FIGS. 4 and 5 are diagrams showing two types of lattice that can be usedfor arranging the cells in an optical component according to theinvention;

FIGS. 6 and 7 are schematic sectional views showing this opticalcomponent at two stages of its manufacture; and

FIG. 8 is a schematic sectional view illustrating another method ofmanufacturing an optical component according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The optical component 10 shown in FIG. 1 is a blank for a spectaclelens. A spectacle lens comprises an ophthalmic lens. The term“ophthalmic lens” is understood to mean a lens that is fitted to aspectacle frame in order to protect the eye and/or correct the sight,these lenses being chosen from afocal, unifocal, bifocal, trifocal andvarifocal lenses.

Although ophthalmic optics is the preferred field of application of theinvention, it will be understood that this invention is applicable totransparent optical elements of other types, such as for example lensesfor optical instruments, filters, optical sight lenses, eye visors,optics for illumination devices, etc. Included within the invention inophthalmic optics are ophthalmic lenses, but also contact lenses andocular implants.

FIG. 2 shows a spectacle lens 11 obtained by cutting the blank 10 arounda predefined outline, shown by the broken line in FIG. 1. In principle,this outline is arbitrary, provided that it falls within the extent ofthe blank. Mass-produced blanks can thus be used to obtain lenses thatcan be adapted so as to fit a large variety of spectacle frames. Theedge of the cut lens may be trimmed without any problem, in aconventional manner, in order to give it a shape matched to thespectacle frame and to the method of fastening the lens to thisspectacle frame and/or for aesthetic reasons. It is also possible todrill holes 14 into it, for example for receiving screws used to fastenit to the spectacle frame.

The general shape of the blank 10 may conform to industry standards, forexample with a circular outline of 60 mm diameter, a convex front face12 and a concave rear face 13 (FIG. 3). The conventional cutting,trimming and drilling tools may thus be used to obtain the lens 11 fromthe blank 10.

In FIGS. 1 and 2, the surface layers have been partially cut away so asto reveal the pixellated structure of the blank 10 and of the lens 11.This structure consists of an array of cells or microcavities 15 formedin a layer 17 of the transparent component (FIG. 3). In these figures,the dimensions of this layer 17 and of the cells 15 have beenexaggerated relative to those of the blank 10 and its substrate 16 so asto make it easier to examine the drawing.

The lateral dimensions D of the cells 15 (parallel to the surface of theblank 10) are greater than 1 micron in order to avoid diffractioneffects in the visible spectrum. In practice, these dimensions arebetween 10 μm and 100 μm. It follows that the array of cells can beproduced using well-controlled technologies in the field ofmicroelectronics and micromechanical devices.

It is therefore possible for the array of cells not to be visible on thelens 11 or on the blank 10. According to the invention, the height h ofthe layer 17 that incorporates the array of cells 15 is preferably lessthan 100 μm, and more preferably between 1 μm and 10 μm inclusive.Advantageously, this height h is about 5 μm.

The walls 18 that separate the cells 15 ensure that they are sealed fromone another. They have a thickness d of between 0.10 μm and 5.00 μminclusive, in particular making it possible to obtain a high fill factorof the optical component. This wall thickness may for example be equalto about 0.35 μm. A high fill factor provides a high effectiveness ofthe desired optical function provided by the substance contained in thecells 15. This fill factor is between 90% and 99.5% inclusive,advantageously between 96% and 98.5% inclusive. By judiciously combiningthe lateral dimension (D) of the cells with the thickness (d) and height(h) of the walls separating the cells, it is possible to obtain anoptical component having a high fill factor, which is not visibledepending on the optical property or properties of the substancescontained in said cells.

For example, with cells arranged in a square lattice (FIG. 4) orhexagonal lattice (FIG. 5), walls 18 with a thickness d=2 μm and pixelsof dimension D=100 μm, only 4% of the area is absorbent (τ≈96%). Forwalls 18 with a thickness d=1 μm and pixels of dimension D=40 μm (ord=0.5 μm and D=20 μm), only about 5% of the area is absorbent (τ≈95%).The lower limit may be about τ=90%.

The honeycomb or hexagonal-type lattice, shown in FIG. 5, is a preferredarrangement as it optimizes the mechanical strength of the array ofcells for a given aspect ratio. However, within the context of theinvention all possible lattice arrangements complying with a crystalgeometry are conceivable. Thus, a lattice of rectangular, triangular oroctagonal geometry can be produced. Within the context of the invention,it is also possible to have a combination of various geometrical latticeshapes in order to form the array of cells, while still respecting thedimensions of the cells as defined above.

The layer 17 incorporating the array of cells 15 may be covered with anumber of additional layers 19, 20 (FIG. 3), as is usual in ophthalmicoptics. These layers provide, for example, such functions as impactresistance, scratch resistance, coloration, antireflection, antifouling,etc. In the example shown, the layer 17 incorporating the array of cellsis placed immediately on top of the transparent substrate 16, but itwill be understood that one or more intermediate layers may be placedbetween them, such as layers providing impact resistance, scratchresistance or coloration functions.

Moreover, it is possible for several arrays of cells to be present inthe multilayer stack formed on the substrate. It is thus possible, forexample, for the multilayer stack to include, in particular, a layerincorporating arrays of cells containing a substance allowing theelement to be provided with photochromic functions and another layerallowing the element to be provided with refractive-index-variationfunctions. These layers incorporating arrays of cells may also bealternated with additional layers as described above.

The various combinations are possible thanks in particular to the greatflexibility of the process for producing the transparent opticalelement. Thus, within the context of the invention, the opticalcomponent may include an array of cells in which each cell is filledwith a substance having one or more optical properties, or else in whichthe array of cells 15 includes several groups of cells containingdifferent substances. The optical component may also consist of a stackcomprising at least two layers incorporating an array of cells, eacharray of cells having identical optical properties, or each array ofcells having different optical properties, or the cells within eacharray of cells having different optical properties.

The transparent substrate 16 may be made of glass or various polymermaterials commonly used in ophthalmic optics. Among the polymermaterials which can be used, one can cite, for information but in anon-limitating purpose, polycarbonate materials, polyamides, polyimides,polysulfons, copolymers of polyethylenterephtalate and polycarbonate,polyolefins, in particular polynorbornens, polymers and copolymers ofdiethylen glycol di(allylcarbonate), (meth)acrylic polymers andcopolymers, in particular (meth)acrylic polymers and copolymers derivedfrom A-bisphonol, thio(meth)acrylic polymers and copolymers, urethaneand thiourethane polymers and copolymers, epoxy polymers and copolymers,and episulfide polymers and copolymers.

The layer 17 incorporating the array of cells is preferably located onits convex front face 12, the concave rear face 13 remaining free inorder to undergo any re-forming operation, by machining and polishing,should this be necessary. However, if the transparent optical element isa corrective lens, the ametropia correction may be achieved by spatiallyvarying the refractive index of the substances contained in the cells15, which makes it possible to dispense with any rework on the rearface, and consequently providing greater flexibility in the designand/or the implementation of the various layers and coatings with whichthe lens has to be provided. The optical component may also be locatedon the concave face of a lens. Of course, the optical component may alsobe incorporated onto a plane optical element.

FIGS. 6 and 7 illustrate a first way in which the array of cells isproduced on the substrate 16. The technique here is similar to thoseused for manufacturing electrophoretic display devices. Such techniquesare described for example in documents WO 00/77570, WO 02/01281, US2002/0176963, U.S. Pat. No. 6,327,072 or U.S. Pat. No. 6,597,340. Thearray of cells can also be produced using fabrication processes derivingfrom microlectronics, well-known to those skilled in the art. By way ofnon-limiting illustration, mention may be made of the processes such ashot printing, hot embossing, photolithography, (hard, soft, positive ornegative), microdeposition, such as microcontact printing, screenprinting, or else ink-jet printing.

In the example in question, a film of a solution of radiation-curable,for example UV-curable, monomers is firstly deposited on the substrate16. This film is exposed to ultraviolet radiation through a mask, whichmasks off the squares or hexagons distributed in a lattice andcorresponding to the positions of the microcavities 15. By selectivecuring, the walls 18 standing up on top of a support layer 21 are leftin place. The monomer solution is then removed and the component is inthe state shown in FIG. 6.

To obtain a similar structure, another possibility is to use aphotolithography technique. This starts with the deposition on thesubstrate 16 of a layer of material, for example a polymer, with athickness of the order of the intended height for the walls 18, forexample 5 μm or 20 μm. Next, a film of a photoresist is deposited onthis layer, this film being exposed through a mask in the form of a gridpattern. The unexposed regions are removed upon developing thephotoresist, in order to leave a mask aligned with respect to thepositions of the walls, through which the layer of material is subjectedto anisotropic etching. This etching, which forms the microcavities 15,is continued down to the desired depth, after which the mask is removedby chemical etching.

Starting from the state shown in FIG. 6, the microcavities 15 are filledwith the substance having an optical property, in the liquid or gelstate. A prior treatment of the front face of the component mayoptionally be applied in order to facilitate the surface wetting of thematerial of the walls and of the bottom of the microcavities. Thesolution or suspension forming the substance with an optical propertymay be the same for all the microcavities of the array, in which case itmay be introduced simply by dipping the component into a suitable bath,using a process of the screen-printing type, a spin coating process, aprocess in which the substance is spread using a roller or a doctorblade, or else a spray process. It is also possible to inject it locallyinto the individual microcavities using an ink-jet head.

The latter technique will typically be adopted when the substance withan optical property differs from one microcavity to another, severalink-jet heads being moved over the surface in order to fill themicrocavities in succession.

However, especially in the case in which the microcavities are formed byselective etching, another possibility is firstly to hollow out a groupof microcavities, to collectively fill them with a first substance, andthen to close them off, the rest of the surface of the componentremaining masked during these operations. Next, the selective etching isrepeated through a resist mask covering at least the regions ofmicrocavities that have already been filled, in addition to the wallregions, and the new microcavities are filled with a different substanceand then closed off. This process may be repeated one or more times ifit is desired to distribute different substances over the surface of thecomponent.

To hermetically seal an array of filled microcavities, anadhesive-coated plastic film is for example applied, this beingthermally welded or hot-laminated onto the top of the walls 18. It isalso possible to deposit onto the region to be closed off a curablematerial in solution, this material being immiscible with the substancehaving an optical property contained in the microcavities, and then tocure this material, for example using heat or irradiation.

Once the array of microcavities 15 has been completed (FIG. 7), thecomponent may receive the additional layers or coatings 19, 20 in orderto complete its manufacture. Components of this type are mass producedand then stored, to be taken up again later and individually cutaccording to the requirements of a customer.

If the substance having an optical property is not intended to remain inthe liquid or gel state, a solidification treatment may be applied toit, for example a heating and/or irradiation sequence, at an appropriatestage after the moment when the substance has been deposited.

In a variant shown in FIG. 8, the optical component consisting of anarray of microcavities 25 is constructed in the form of a flexibletransparent film 27. Such a film 27 can be produced by techniquessimilar to those described above. In this case, the film 27 can beproduced on a plane substrate, i.e. one that is not convex or concave.

The film 27 is for example manufactured on an industrial scale, with arelatively large size, in order to make savings in the combinedexecution of the steps of the process, and then it is cut to theappropriate dimensions in order to be transferred onto the substrate 16of a blank. This transfer may be carried out by adhesively bonding theflexible film, by thermoforming the film, or even by a physical adhesioneffect in a vacuum. The film 27 may then receive various coatings, as inthe previous case, or may be transferred onto the substrate 16 which isitself coated with one or more additional layers as described above.

In one field of application of the invention, the optical property ofthe substance introduced into the microcavities 15 is its refractiveindex. The refractive index of the substance is varied over the surfaceof the component in order to obtain a corrective lens. In a firstembodiment of the invention, the variation may be produced byintroducing substances of different indices during the manufacture ofthe array of microcavities 15.

In another embodiment of the invention, the variation may be achieved byintroducing into the microcavities 15 a substance whose refractive indexmay be subsequently adjusted by irradiation. The writing of thecorrective optical function is then carried out by exposing the blank 10or the lens 11 to light whose energy varies over the surface in order toobtain the desired index profile, so as to correct the vision of apatient. This light is typically that produced by a laser, the writingequipment being similar to that used for etching CD-ROMs or otheroptical memory media. The greater or lesser exposure of thephotosensitive substance may result from a variation in the power of thelaser and/or of the choice of the exposure time.

Among the substances that can be used in this application, mention maybe made, for example, of mesoporous materials and liquid crystals. Theliquid crystals may be frozen by a polymerization reaction, for exampleone induced by irradiation. Thus, they may be frozen in a chosen statein order to introduce a predetermined optical retardation in thelightwaves that pass through them. In the case of a mesoporous material,the refractive index of the material is controlled through the variationin its porosity. Another possibility is to use photopolymers that havethe well-known property of changing its refractive index over the courseof the irradiation-induced curing reaction. These index changes are dueto a modification of the density of the material and to a change in thechemical structure. It will be preferable to use photopolymers thatundergo only a very small volume change during the polymerizationreaction.

The selective polymerization of the solution or suspension is carriedout in the presence of radiation that is spatially differentiated withrespect to the surface of the component, so as to obtain the desiredindex variation. This variation is determined beforehand according tothe estimated ametropia of a patient's eye to be corrected.

In another application of the invention, the substance introduced inliquid or gel form into the microcavities has a photochromic property.Among the substances used in this application, mention may be made, byway of examples, of photochromic compounds containing a central unitsuch as a spirooxazine, spiro-indoline-[2,3′ ]benzoxazine, chromene,spiroxazine homoazaadaman-tane, spirofluorene-(2H)-benzopyrane ornaphtho[2,1-b]-pyrane core such as those described in particular in thePatents and Patent Applications FR 2 763 070, EP 0 676 401, EP 0 489655, EP 0 653 428, EP 0 407 237, FR 2 718 447, U.S. Pat. No. 6,281,366and EP 1 204 714.

Within the context of the invention, the substance having an opticalproperty may also be a dye, or a pigment capable of modifying the degreeof transmission.

1. Process for producing a transparent optical element, comprising thefollowing steps: producing an optical component having at least onetransparent array of cells that are juxtaposed parallel to one surfaceof the component, each cell being hermetically sealed and containing asubstance having an optical property; and cutting the optical componentalong a defined contour on said surface, corresponding to apredetermined shape of the optical element.
 2. Process according toclaim 1, wherein the array of cells constitutes a layer having,perpendicular to said surface, a height of less than 100 μm.
 3. Processaccording to claim 1, which furthermore includes a step of drillingthrough the optical component in order to fasten the optical element toa holding support.
 4. Process according to claim 1, wherein theproduction of the optical component comprises the formation of the arrayof cells on a rigid transparent substrate.
 5. Process according to claim1, wherein the production of the optical component comprises theformation of the array of cells within a flexible transparent filmfollowed by the transfer of said film onto a rigid transparentsubstrate.
 6. Process according to claim 1, wherein the substance havingan optical property contained in at least some of the cells is in theform of a liquid or gel and the production of the optical componentcomprises the formation, on a substrate, of a grid of walls for definingthe cells parallel to said surface of the component, the collective orindividual filling of the cells with the substance having an opticalproperty in the form of a liquid or gel, and the closing of the cells ontheir opposite side from the substrate.
 7. Process according to claim 1,wherein the optical property is chosen from a coloration, photochromism,polarization or refractive-index property.
 8. Process according to claim1, wherein different cells contain substances having a differentrefractive index.
 9. Process according to claim 8, wherein thesubstances having a different refractive index comprise photopolymers,liquid crystals or mesoporous materials.
 10. Process according to claim9, wherein the production of the optical component comprises theformation, on a substrate, of a grid of walls for defining the cellsparallel to said surface of the component, the collective filling of thecells with a solution or a suspension of monomers or liquid crystals,the closing of the cells on their opposite side from the substrate, andthe selective curing of said solution or suspension in the presence ofdifferentiated electromagnetic radiation parallel to said surface of thecomponent.
 11. Process according to claim 8, wherein the refractiveindex of the substances contained in the cells are adapted in order tovary said index over the surface of the component according to theestimated ametropia of an eye to be corrected.
 12. Process according toclaim 1, wherein the array of cells includes several groups of cellscontaining different substances.
 13. Process according to claim 12,wherein the production of the optical component comprises the formation,on a substrate, of a grid of walls for defining the cells parallel tosaid surface of the component, the differentiated filling of the cellswith the substances having an optical property, using ink-jet heads, andthe closing of the cells on their opposite side from the substrate. 14.Process according to claim 1, wherein several arrays of cells arestacked on the thickness of the component.
 15. Process according toclaim 14, wherein each array of cells has identical optical properties,or each array of cells has different optical properties, or the cellswithin each array of cells have different optical properties. 16.Process according to claim 1, wherein the fill factor τ is greater than90%, parallel to the surface of the component.
 17. Process according toclaim 1, wherein the cells of the array are arranged in a hexagonal-typelattice.
 18. Process according to claim 1, wherein the cells havedimensions of greater than 1 μm parallel to the surface of thecomponent.
 19. Process according to claim 1, wherein the cells areseparated by walls having dimensions of between 0.10 μm and 5 μmparallel to the surface of the component.
 20. Process according to claim19, wherein the walls (18) have dimensions of less than 0.35 μm. 21.Process according to claim 19, wherein the cells are separated by wallsmade of a material that does not reflect light and have dimensions ofbetween 0.40 μm and 3.00 μm.
 22. Process according to claim 21, whereinthe walls have dimensions of between 0.40 μm and 1.00 μm.